The field of art to which the invention pertains includes the art of measuring and testing as directed to a socket-to-casing construction of a pressure gauge.
Pressure gauges enjoy very extensive commercial and industrial use and are consequently regarded as high production items. Because of such wide use, they are supplied by a plurality of manufacturers and sold in very price conscious competition. Each manufacturer instinctively strives to reduce product costs by improvements, however marginal, which reduce labor and/or materials that could contribute to cost savings in the end product.
Commonly affording pressure sensitivity in the pressure gauge is a Bourdon tube of a pressure tight construction having a free end displaceably movable in response to pressure changes supplied at its inlet. To translate tube displacement into values of pressure, a geared movement or the like is connected between the free end of the Bourdon tube and a pointer. The pointer in turn is advanced by the movement relative to a calibrated dial face in correlation with changes in pressures of a measured condition. As typically constructed, pressure being measured is communicated via a bored stem and socket to the inlet end of the Bourdon tube. The socket extends through an aperture in the casing which encloses these components with clearances that enable the various operative displacements to be performed.
Whether the socket extends through the back or bottom of the casing, it is customary to secure the operating components in their final placement by means of one or more fastener screws attaching a raised wall of the socket against an internal surface of the casing. Unfortunately, however, it has been found that such gauges when installed in service occasionally encounter percussive blows inflicted inadvertently by passing objects, mishandling or the like, of magnitude sufficient to bend the casing into an offset relation with its contents. When this occurs, the stem axis becomes tilted or canted relative to the internal walls of the casing posing a problem that can be potentially acute where the casing is of relatively soft material such as plastic or thin sheet metal stock. Where the extent of bending offset between socket and casing is sufficient to place the operating mechanism and the surrounding internal surfaces of the casing into an interference contact, operational accuracy of the instrument, if in fact still operational, can be deleteriously affected to a large degree.
A problem of the foregoing type represents not only a potential hazard from inoperation or inaccurate information provided by the gauge but can and frequently is regarded by the owners of such gauges as reflecting adversely on the quality of the gauge manufacture. In order to preclude against either of these possibilities, it has been necessary therefore to somehow reinforce the rigidity of the casing in the area about the fastened components by such obvious approaches as increased casing thickness, increased number of fasteners, etc. While either of the latter can, of course, be considered a solution to the immediate problem of increasing resistance to case bending, both represent relatively expensive solutions adding significantly to the cost of an otherwise highly cost conscious product. A construction for increased unidirectional rigidity is known and has proven helpful but has been ineffective if the inflicted blow is opposite in direction to that being provided against. Despite recognition of the foregoing, a ready solution has not heretofore been known.